Unnecessary To the email already included in the Mailing list

When one send mail to the mailing list, it is not necessary to fill any mail addresses in the To / CC / Bcc field if those email addresses are already in the mailing list.

Our mailing list system is based on GMAIL service, it is almost the best service in the industry: Fast, Robust, Intelligent...

What's the Intelligent side?
(1) It only send one copy to multiple email addresses related with each other. Such as forward in serial, forward to itself...
(2) Spam / junk mail control

If you fill one's mail address in the To / CC / Bcc field when the email address is already in the mailing list, then one may get more than one copy of the same mail. Most time it is not necessary.

Sure you still can do so if you think it is necessary.